This invention relates to an apparatus for controlling an internal combustion engine operable on gasoline fuel or gasoline/alcohol fuel blend.
For example, Japanese Patent Kokai No. 56-98540 discloses an apparatus for controlling an internal combustion engine operable on gasoline fuel or gasoline/alcohol fuel blend. The engine control apparatus employs an oxygen sensor sensitive to the oxygen content in exhaust gases discharged from the engine for providing a closed loop air/fuel ratio control and an alcohol concentration sensor sensitive to the alcohol concentration of the fuel delivered to the engine. The sensed alcohol concentration is used in calculating appropriate values for fuel delivery requirement in the form of fuel-injection pulse-width and ignition-system spark timing.
However, such a conventional engine control apparatus will fail to calculate appropriate values for fuel delivery requirement and ignition-system spark timing., resulting in unstable engine operation in the event of failure of the alcohol concentration sensor.